v0.2.0

• Added support for images, using standard Markdown syntax.
• Added support for multi-paragraph descriptions, questions, choices, and
  feedback.
• Added support for essay questions.
• Added support for numerical questions.
• Added support for question groups. A subset of the questions in a group is
  chosen at random when a quiz is taken.
• Added support for executable code blocks. These can be used to generate
  questions automatically. This feature requires the command-line flag
  --run-code-blocks or setting run_code_blocks = true in the config
  file.
• Quiz titles are now processed as plain text, rather than as Markdown,
  because QTI does not support HTML titles.
• Fixed a bug that prevented source file names from appearing in error
  messages. Fixed misspelling of "imsmanifest.xml" in QTI output.